Stator structure



Jan. 23, 1968 H. LYNCH Em. 3,365,173

STATOR STRUCTURE Original Filed Feb. 2S, 1966 '35uv Af T fuk? United States Patent O 3,365,173 STATR STRUCTURE Henry E. Lynch, `loseph S. Alford, and William Bowles Campbell, Cincinnati, Ghia, assguors to General Electric Company, a corporation of New York Continuation of application Ser. No. 530,432, Feb. 28, 1966. This application Dec. 16, 1966, Ser. No. 602,426 9 Claims. (Cl. 253-78) This is a continuation-in-part of application Ser. No. 530,432 tiled Feb. 28, 1966, now abandoned.

The present invention relates to turbomachinery stator structure and, more particularly, to an improved segmented turbine nozzle structure as may be used in jet engines.

One of the general nozzle diaphragm structure as used in jet engines has been to weld a series of vanes, which can be cast or fabricated, into circular bands and make large segments of vanes. Such segmented structures may employ any number of vanes secured between the cornplete circular bands for segmented bands. O ne of the problems with such a structure is the serviceability. The elements crack, the bands crack, and replacement is often necessary. When fabricated vanes are used, there are erosion problems generally of the leading edge and eating into the cavity in the center of the vanes. As a result, the serviceability and maintainability problems are severe. The segmented arrangements are diicult to disassemble and are expensive. It there is one defective in a baud or segment of numerous vanes, it is costly to disassemble an replace that one vane.

In present day jet engines, where the life of the parts is required to be extremely longup to three or four times the life of similar parts heretofore-it is necessary to have a complete new design that meets the objectives of long life, easy maintainability, and easy replacement.

The main object of the present invention therefore iS to provide turbomachinery stator structure that meets the objectives of long life, easy maintainability, and easy replacement.

A further object is to provide a segmented nozzle structure which is inherently strong because of a box-like configuration and is provided in smaller elements that are easily and individually replaceable.

Another object is to provide such a segmented nozzle structure which is especially useful in a multi-stage turbomachinery environment for easy replacement of any individual stage without the necessity of tear down of all the stages.

A further object is to provide such a structure in which the nozzle segments and shrouds form an interlocking and mutually supportable arrangement allowing for easy assembly `and disassembly for individual replacement.

A further object is to provide such a structure which may be assembled or disassembled with virtually no tools and in which some of the components of the nozzle segments form dual functions avoiding the need for additional complex structure.

Briey stated, the invention discloses a turbine nozzle structure which includes a casing for the flow of the eX- haust gases therethrough in the conventional manner. The casing is provided with a series of axially spaced and peripherally directed circumferential rings around the inner surface. Each of the rings has axial slots in its aft surface substantially parallel to the casing and each alternate ring also has a radial slot forward of its respective axial slot. A nozzle segment that includes at least two airfoils joined by top and bottom platforms into a box structure is provided. The top platform has forward and aft rails that extend peripherally and the forward rail has an axial slot in its forward surface parallel to the casing for engaging one of the rings aft slots and radially locate the nozzle segment. The aft rail also has an axial parallel slot in its aft surface and the aft rail is disposed in the radial slot of the alternate rings for axially locating the nozzle segment. Stop means is provided between the casing and segment for locating the segment peripherally. Shroud means is provided downstream of each segment, the shroud having a forward lip which is disposed in the aft rail slot to hold the shroud in position and radially locate the segment whereby the segments are rotatable into position 4in the rings in the casing and are interlocked with lthe shroud. The nozzle segments may be made conveniently in two airfoil sections and the interlocking shrouds may span several segments. The bottom platform of the nozzle segment is provided with a tang, that may be scalloped for lightness, that extends radially inwardly and has attachment means to carry seal structure.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed lthe invention will be better understood from the following description taken in connection with the accompanying drawing, in which:

FIGURE 1 is a general view of a typical gas turbine engine illustrating the environment of the invention,

FIGURE 2 is a perspective view of a typical nozzle segment,

FIGURE 3 is a partial perspective exploded view of the casing and shroud structure,

FIGURE 4 is a partial perspective illustrating the rotation of the nozzle segment into the casing,

FIGURE 5 is a partial perspective of a segment in position and the interlocking arrangement of a shroud,

FIGURE 6 is a view similar to FIGURE 5 showing the shroud in position locking the parts together, and

FIGURE 7 is a partial cross sectional vview of the shroud and segment interlocked in the casing and showing the peripheral stop.

Referring first to FIGURE l, there is illustrated a general configuration of a jet engine 10 of the usual conventional type. The stator structure of the present invention will be described in connection with a turbine nozzle diaphragm although it might be usable in the compressor structure as well. In such an engine, the turbine nozzles are located at 12 aft of the combustor 14 and spanning a turbine wheel 16 with the usual exhaust nozzle downstream. The invention is the structure l2 as it will preferably be used in a multi-stage turbine comprising several turbine wheels 16 although is not limited to multi-stage turbines. The nozzle or diaphragm structure 12 is supported from a thin casing 18. This generally is the setting of the detailed structure to follow.

Since extremely long life is required in present engines, it is necessary to provide a structure that is strong enough to withstand thousands of hours of use and yet is easily serviced and easily replaceable when necessary. Additionally, it is desired to provide such structure with the minimum amount of tear down in multi-stage turbines and with the minimum tools required. To this end, the present invention provides individual nozzle segments as shown generally at 20 in FIGURE 2. The individual nozzle segment 20 may be made of numerous vanes, but for easy replacement and high strength as Well as good serviceability, it is preferably made in pairs of airfoils as shown. Each segment then comprises a pair of spaced airfoils 22 which guide the exhaust gases to turbine buckets 16 in the usual fashion. In order to provide strength, the airfoils are joined by top and bottom platforms 24 and 26 respectively. The individual nozzle segment 20 thus comprises a box-like very rigid and strong structure with the airfoils 22 forming the sides of the box as well as the guiding nozzles for the exhaust gases. It will be appreciated that bottom platform 26 may be as shown or may have skewed edges depending on the angle of the airfoils as is well known in the art. For simplicity, a generally rectangular platform is shown.

In order to provide attachment means for the individual segments 20, the rela-tively thin casing 18, as shown in FIGURE 3, is provided with a series of axially spaced and peripherally directed circumferential rings 28 and 30. Each of these rings is provided with an aft directed axial slot 32 and 34 in the aft surface of the respective ring and each slot is parallel to the casing 18 as shown. For a purpose to be described, each alternate ring 30 also is provided with a radial slot 36 forward of its axial slot. This ring structure provides the primary locating structure on the casing 18 into which the individual nozzle segments 20 are to be disposed. It will be understood that upstream of ring 28 and downstream of ring 34 there may normally be rotating turbine buckets such as 16 in FIGURE l. For good sealing of the rotating structure, shroud means 3S is provided downstream of each nozzle segment and plural shrouds are provided in multi-stage turbines as seen in the exploded view in FIGURE 3. These will be explained in more detail later.

In order to attach the individual nozzle segments 20 to the casing, each segment has its top platform 24 provided with forward and aft rails 40 and 42 respectively. These rails extend peripherally of the platform as shown and it is to be understood that a large number of the inlividual nozzle segments will be placed edge to edge to form a complete circle upstream of each turbine wheel 16. These rails will generally form part of the casing and may be supported for extra rigidity by suitable webbing 44. In order to support nozzle segments 20 in the casing 18 both radially and axially, the forward rail is provided with an axial slot 46 in its forward surface which slot is also parallel to the casing and which is designed to overlappingly engage with slot 32 of ring 28 as will be apparent. Similarly, the aft rail 42 has an axial parallel slot 48 in its aft surface for interlocking with the shroud 38 as will appear.

Referring to FIGURE 4, there is shown the rotation of the nozzle segment 20 into the casing. The individual segment 20 is placed in position whereby the slot 46 in the forward rail is hooked into the slot 32` in ring 28 of the casing as clearly shown. This partially locates the nozzle segment radially in the casing. The segment is rotated in the direction shown by 4the arrow at the bottom of FIGURE 4 up into a flush position with the casing as shown in FIGURES 5-7. Such rotation disposes the aft rail 42 in the radial slot 36 to axially locate the segment in the casing. At this point if, as is customary, the segments are installed with the casing in a vertical position, it will be apparent that the segments are now held axially in position in the casing and extend radially inward of the casing. However, in the horizontal position of the casing the segments would rotate back down to the position shown in FIGURE 4 and those on the top would drop out.

The segments, having been radially and axially located by the structure thus described, must now be peripherally located and this is done by suitable stop means 50 between the casing and nozzle segment and this may comprise any suitable stud-like member, such as the nut and bolt arrangement shown, which extends through the casing 18 at radial slot 36 and into a convenient recess 52 in the aft rail 42. Any stop structure may be used and the nut and bolt arrangement shown merely provides a convenient execution where a square head 54 may tit recess 52 without further structure and nut 56 then cornpletes the stop.

Each segment is now located in all three directions. radially, axially and peripherally. However, the overlapping engagement of the slots 32 and 46 provides a loose t as will be apparent. Since shroud structure 38 is required for the rotating buckets, it is convenient to use this shroud structure as an interlocking memebr. The shroud 38 may contain the usual honeycomb or its equivalent 58 and the shroud bands 38 may extend over several segments for convenience. Each shroud 38 is provided with a forward lip 60, as shown in FIGURES 5-7, which is disposed in the ring parallel slot 34 to overlap and engage the shroud in a tongue-and-groove arrangemnt. This holds the shroud in position in the casing and radially locates the segment by the interengagement of the bottom portion 62 of the lip with the overlapping protion of aft rail 42. The completely assembled structure is shown in FIG- URE 6 and it can be seen that the segment is rotated into position in the casing rings and is interlocked with the shroud downstream of the individual segment. Of course, this is duplicated and a similar shroud is provided as shown in FIGURE 3 for the next upstream turbine in a multi-stage arrangement.

Inasmuch as the shroud structure usually spans several segments but not a complete half casing on an engine that has a split casing, it is necessary to provide means whereby the multiple segments may all abut one another to provide a complete circular nozzle diaphragm. To this end, several segments may be rotated into position as previously described, the shroud 38 slid into its respective slot 34 to interlock the rotated segments and may span several segments. Each of the segment aft rails 42 is provided with a cut-out 64 at one end which cut-out may be merely milled into the end of the rail and the shroud lip bottom portion is provided with a tab 66 to nest llush in the cut-out as shown in FIGURE 6. For example, three nozzle segments 20 may be rotated into the casing, a shroud segment 38 spanning three segments is then slid into its recess 34 and abutted tlush against the last segment with tab 66 disposed in recess 64. Then three more segments may be abutted directly against the last segment, since there are no protrusions due to the nesting relation, and the process repeated. Depending on the squared or skewed shape of platform 26, the recess 34 may be at one or the other end of rail 42.

Since the nozzle segments generally support sealing structure in one form or another, the bottom platform 26 is provided with a radially extending tang 68 that is provided with any attachment means 70 as shown in FIG- URE 4. The attachment means is used to connect with a ring 72 on either side thereof or its equivalent which may support sealing structure to seal between turbine stages of the rotor. For lightness, since the tang 68 is merely a support, it may be scalloped as seen in FIGURE 2 to cut away the unnecessary metal and avoid a complete ring around the bottom of the assembled segments.

It is generally customary to make the engine casing in halves bolted along a horizontal flange and the structure thus described is especially suitable to such an installation. It will be apparent that no tools are required for assembly or disassembly of the nozzle diaphragm segments. A wrench may be required to complete the installation of attachment means 70 and nut 56 but the main and complete installation is completely without tools. Also, the various slots described may be sized for snug fitting in the overlapping engagement with the shroud structure and it will be seen that, for example, the front slot 46 on rail 40 not only locates the nozzle segment radially but provides the recess for supporting the aft end of the nozzle shroud for the turbine stage upstream. The shroud, in turn, tends to lock and securely fasten the nozzle segment in position. Easy access is had to any segment by merely sliding out the necessary shrouds until the segment desired is reached which segment may then be rotated out of position as shown in FIGURE 4 and replaced with another segment and this may be accomplished without the need, in a multi-stage arrangement, of removing adjacent stages.

While there has been described a preferred form of the invention, obvious equivalent variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims,

the invention may be practiced otherwise than as specifically described, and the claims are intended to cover such equivalent variations.

We claim:

1. Turbomachinery stator structure comprising:

a casing for the flow of iiuid therethrough,

a plurality of axially spaced-apart and peripherally directed rings extending inwardly of said casing, said plurality of rings including a first ring having a circumferentially extending aft directed slot therein and a second ring having both a circumferentially extending aft directed slot therein and a circumferentially extending radially directed slot therein forward of the aft directed slot, said second ring being located aft of said first ring,

an annular stator vane assembly disposed within said casing between said first and second rings, said stator vane assembly including a plurality of abutting stator vane segments each comprising radially disposed airfoil structure and an arcuate outer platform secured thereto,

said outer platform including forward and aft peripherally directed rails extending outwardly therefrom, said forward rail having a forwardly directed slot ytherein and said aft rail having an aft directed slot therein,

the slots of said first ring and said forward rail interengaging to support the forward end of said stator vane segment within said casing and the aft rail engaging the radially directed slot of said second ring to axially locate said stator vane segment,

and an arcuate shroud member extending aft of said second ring, said shroud member including forwardly directed lip means engaging the aft directed slots of both said second ring and said aft rail to support both the aft end of said stator vane segment and the forward end of said sh-roud member within said casing.

2. Turbomachine stator structure as defined by claim 1 further comprising stop means interconnecting said casing and said stator vane segment to prevent peripheral movement of said stator vane segment within said casing.

3. Turbomachine stator structure as defined by claim 2 wherein said shroud member aft of said second ring arcuately spans a plurality of stator vane segments.

4. Turbomachine stator structure as defined by claim 3 wherein said shroud member aft of said second ring has a tab at one end thereof projecting forwardly therefrom and wherein the stator vane segment aligned with said tab has a cut-out at one end of its aft rail for receiving said tab to interlock said shroud member and the stator vane segment and thereby prevent peripheral movement of said shroud member within said casing, said tab and said cut-out being dimensioned for fiush nesting of said tab within said cut-out to permit abutment of adjacent stator vane segments.

5. Turbomachine stator structure as defined by claim 2 wherein the aft rail of each outer platform has a recess therein, said stop means comprising a bolt extending through said casing into the radially directed slot of said second ring and said recess.

6. Turbomachine stator structure as defined by claim 5 wherein said shroud member aft of said second ring arcuately spans a plurality of stator vane segments.

7. Turbomachine stator structure as defined by claim 6 wherein said shroud member aft of said second ring has a tab at one end thereof projecting forwardly therefrom and wherein the stator vane segment aligned with said tab has a cut-out at one end of its aft rail for receiving said tab to interlock said shroud member and the stator vane segment and thereby prevent peripheral movement of said shroud member within said casing, said tab and said cut-out being dimensioned for iiush nesting of said tab Within said cut-out to permit abutment of adjacent stator vane segments.

8. Turbomachine stator structure as defined by claim 7 further comprising an arcuate inner platform secured to the radially disposed airfoil structure of said stator Vane segment, said inner platform having a scalloped tang extending radially therefrom with attachment means thereon for supporting sealing structure.

9. Turbomachine stator structure as defined by claim 8 wherein the annular stator vane assembly is a turbine nozzle diaphragm.

References Cited UNITED STATES PATENTS 2,834,537 5/1958 Neary. 2,945,673 7/1960 Hockert et al. 2,971,743 2/ 1961 Welsh. 3,070,35 3 12/ 1962 Welsh. 3,182,955 5/1965 Hyde.

EVERETTE A. POWELL, IR., Primary Examiner. 

1. TURBOMACHINERY STATOR STRUCTURE COMPRISING: A CASING FOR THE FLOW OF FLUID THERETHROUGH, A PLURALITY OF AXIALLY SPACED-APART AND PERIPHERALLY DIRECTED RINGS EXTENDING INWARDLY OF SAID CASING, SAID PLURALITY OF RINGS INCLUDING A FIRST RING HAVING A CIRCUMFERENTIALLY EXTENDING AFT DIRECTED SLOT THEREIN AND A SECOND RING HAVING BOTH A CIRCUMFERENTIALLY EXTENDING AFT DIRECTED SLOT THEREIN AND A CIRCUMFERENTIALLY EXTENDING RADIALLY DIRECTED SLOT THEREIN FORWARD OF THE AFT DIRECTED SLOT, SAID SECOND RING BEING LOCATED AFT OF SAID FIRST RING, AN ANNULAR STATOR VANE ASSEMBLY DISPOSED WITHIN SAID CASING BETWEEN SAID FIRST AND SECOND RINGS, SAID STATOR VANE ASSEMBLY INCLUDING A PLURALITY OF ABUTTING STATOR VANE SEGMENTS EACH COMPRISING RADIALLY DISPOSED AIRFOIL STRUCTURE AND AN ARCUATE OUTER PLATFORM SECURED THERETO, 